单项选择题A.He lost a button at work.B.He doesn’t know where he put the calculator.C.He thinks he broke something the woman lent him.D.He’s not sure how to solve the math problem.
单项选择题A.It is more comfortable than a conventional train.B.It doesn’t require much track maintenance.C.It doesn’t remain in any station very long.D.It carries more passengers than a conventional train.
单项选择题A.It uses nuclear energy.B.It rests on a cushion of professional air.C.It flies over magnetically activated tracks.D.It uses a device similar to a jet engine.
单项选择题A.To learn how to prevent a bone disease.B.To understand differences between bone tissue and other tissue.C.To find out how specialized bone cells have evolved.D.To create artificial bone tissue.
单项选择题A.A stormy ocean.B.Calm water.C.Golden sand.D.Little waves.